Some printing systems form printed images on rolls of paper or other print media. The media is pulled from a roll and ink images are formed on the media as the media passes through the printer. The printed media can be rolled into a take-up roll for removal from the printer or cut into individual sheets by a cutter that directly follows the printer. The take-up can be loaded into another apparatus that cuts the roll into individual sheets. Some media rolls are blank prior to be printed, while other rolls include existing markings, such as letterheads, logos, watermarks, and pre-printed form fields. For example, many such documents of this latter type include a pre-printed layout and the printer fills in each page with text, graphics, and any printed image that aligns with the existing markings on the print medium. Additionally, some media rolls include perforations that enable efficient separation of the individual pages of the roll after completion of the printing process.
During a printing operation, the printer forms printed images on each page in the media roll. The print medium moves through a print zone in a process direction to receive the printed images. Without proper registration in the process direction, however, the printed images may not properly align with each page. For example, printed text may appear in an incorrect position that does not align with markings in a pre-printed form. For severe misalignments, the printer may print an image that crosses a perforated edge between two different pages formed in the media roll instead of printing within a single page. While manual alignment of the print medium with the printer at the beginning of the print job can help produce accurately aligned images, variations in the print medium and movement in the print medium during the printing process result in process direction errors that increase over time during the printing process. Eventually, the errors may grow large enough that the printed pages have unacceptable alignment errors, which results in wasted paper and requires printer down time to realign the printer manually. Consequently, improvements to the alignment of printed images with pages formed in the print medium to maintain proper alignment during a printing process would be beneficial.